Because of its resistance to corrosion and erosion, its superior heat transmission capabilities, and because of its tendency to resist the deposition of particulate matter thereon, cast iron has long been deemed a superior constituent of recuperative heat exchangers.
Previous patent art including U.S. Pat. Nos. 1,992,097, 2,537,276, and U.K. Pat. No. 1,197,409 is directed to arrangements that utilize various forms of cast iron plates held together by a multiplicity of longitudinal bolts. The individual plates of the heat exchanger are assembled by hand, bolts are inserted through holes in the plates, and fastening means such as nuts are individually placed thereon to provide an assembled unit. A gasket material such as asbestos rope is commonly positioned between cast halves of the recuperator before they are bolted together to provide a seal that precludes the flow of fluid between abutting recuperator halves.
Such a manufacturing process is slow and it requires excessive amounts of manpower to laboriously assemble and properly connect the separate parts of the heat exchanger into an integral unit. Moreover, the holes through the several plates seriously weaken them to require additional reinforcement that adds even more to the cost and weight of the heat exchanger. Casting a heat exchanger of the type defined as independent halves is, however, a procedure necessitated by the intricate interior configuration and the great size of a completed unit.